Former astronaut Marc Garneau crowned Justin Trudeau the next leader of the Liberal party Wednesday, weeks after warning Grit stalwarts against handing the sceptre to an untested candidate.

But now, according to Garneau, the former drama teacher has more than just sizzle to lead a tattered party still reeling from its historic shelling in the 2011 election under Michael Ignatieff.

With Garneau's candidacy crashing to Earth, Trudeau, who moonlights as a professional speaker and charges upwards of $20,000 a script, is now the shoo-in favourite to become the party's next chief April 14.

Garneau's sudden exit and endorsement of his fellow Montreal MP surprised many, as did his pronouncement he was in second place among the eight contenders, but still chose to quit.

"Numbers don't lie ... The numbers indicate very clearly that Justin is the overwhelming favourite," Garneau said at a news conference.

"I will work for him as a loyal Liberal when he becomes the leader of the party."

Other camps disputed the engineer's math and said they were in it to win it.

"If that's what Marc is counting on for now to bow out that's OK. The rest of us don't accept the data," said Jamie Carroll, campaign manager for Vancouver MP Joyce Murray, who believed they were ahead of Garneau before he resigned.

Garneau dropped out before the muddled party decided whether it would heed calls from Trudeau's team to grant an extension to Thursday's deadline for supporters to register to vote for the leader.

Last week the party boasted that nearly 300,000 supporters were ready to participate in the leadership, but less than 90,000 had registered at the start of the week to join the process -- causing much angst and red faces among party officials.

The party faces criticism for its inability to process and identify supporters and charges that if it can't manage a leadership race how can it manage a national campaign or even govern.

Many believe that moving the registration goal line would benefit Trudeau because he has the money and volunteers to woo supporters over other camps to seal the deal, including a stalled Garneau campaign had he stayed put.

But if Trudeau fails to pull off a snap win, that could open the door to Murray, who also has a solid organization behind her, and other candidates' Martha Hall Findlay, Karen McCrimmon, David Bertchi, Martin Cauchon and Deborah Coyne.